Safety device for crane boom



March 24, 1970 J. TAMBORINO SAFETY DEVICE FOR CRANE BOOM 4 Sheets-Sheet 1 Filed July 2'7, 1967 I N VENTOR. Jam 5004/0 J. TAMBORINO SAFETY DEVICE FOR CRANE BOOM March 24, 1970 .4 Shets-Sheet 2 Filed July 27, 1967 INVENTOR. fwfm/ 75%500/1 0 M 7 045M! 541% March 24, 1970 .1. TAMBORINO SAFETY DEVICE FOR CRANE BOOM 4 Sheets-Sheet 3 Filed. July 2?, 1967 Rm [/Wm mm M illlllllll Illlll March 24, 1970 J. TAMBORINO SAFETY DEVICE FOR CRANE BOOM .4 Sheets-Sheet 4 Filed July 27, 1967 INVENTOR. fwm/ flwam/o BY #ZM flrme/z United States Patent Office 3,502,228 Patented Mar. 24, 1970 3,502,228 SAFETY DEVICE FOR CRANE BOOM Joseph Tamborino, 235 S. Beach Blvd., Space 90, Anaheim, Calif. 92804 Filed July 27, 1967, Ser. No. 656,397 Int. Cl. B66c 13/48, 23/06 US. Cl. 212-39 16 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention relates to boom cranes and more particularly to a boom crane provided with safety means to restrain the boom from pivoting when the means for raising and lowering the boom fail.

State of the prior art The construction industry employs a number and variety of boom cranes for hoisting construction material. Generally these cranes include cable, drums, brakes and a platform to which one end of the horn is pivotally secured. An opposite and free end of the boom carries a peak sheave over which the load carrying cable is guided. A suitable swivel and hook is secured to the free end of the cable. The other end of the cable is secured to a hoisting drum. One end of an extender cable is secured to the free end of the boom, and the other end of the extender cable is attached to a bridle. One end of a draw cable is connected to the bridle, and the other end is connected to a draw drum mounted on the platform. When the draw cable is retracted, the bridle is moved towards the platform and the boom is pivoted upwardly. The effective height of the crane as well as the horizontal position of the hook arethereby changed.

The draw cable is frequently extended or retracted since this is often the most convenient manner in which the horizontal position of the book can be changed. The rough treatment to which cranes are generally subjected around construction sites puts heavy loads and a substantial amount of wear onto the draw cable. It is often released at a rapid rate and is instantaneously stopped whereby a substantial amount of kinetic energy, which results from the pivotal downward movement of the boom, subjects the draw cable to extensive loads. Frequently, the draw cable breaks under such heavy loads after it has become worn.

A broken draw cable permits the boom to drop freely with its weight and any load suspended on the hook at ,7

SUMMARY OF THE INVENTION Briefly, this invention provides a crane including a platform, a raisable boom having one end pivotally secured to a plateform, an extender cable secured to the boom adjacent the free end of the boom, means for raising and lowering the boom and bridle means including a bridle shaft for coupling the extender cable and the draw cable with an elongated safety bar which is connected with the platform. The safety bar extends past adjacent the bridle shaft and is provided with a plurality of longitudinally spaced dogs facing toward the bridle shaft. Means are included for biasing the safety bar towards the bridle shaft such that the dogs on the safety bar may be caused engage the bride shaft by the operator if the means for raising or lowering the boom should fail. There are means for biasing the safety bar in opposition to the means for biasing the safety bar towards the bridle shaft such that the safety bar and the bridle shaft are normally disengaged when the crane is being used. The means for biasing the safety bar in opposition are operatively connected with brake means in the crane and are disabled in response to application of the brake means by the operator.

This invention provides virtually fail-safe safety features for a boom crane such that the boom is restrained from pivoting towards the ground when the brake means are applied. Normally, the craneoperator must exercise a positive control to remove the brake means and operate the crane. If the draw cable or the means actuating the draw cable should fail, the application of the brake means and operate the crane. The danger of injury to health or property, including the crane itself, from a falling boom is thereby substantially eliminated. If the draw cable fails, the crane is out of operation for only such length of time as it takes to replace or repair the draw cable. Since the replacement of the draw cable is a relatively minor repair, requiring not much time, the down time of the crane and with it the idleness of the workmen requiring the services of the crane and of other equipment, is substantially reduced.

The means for biasing the safety bar in opposition are preferably actuated from centrally located controls of the crane as pointed out above. Although the means can be constructed to be actuated independently from other controls, by the operator, in the preferred embodiment of this invention they are directly coupled to the brake means constituting part of the controls for activating and deactivating the draw cable. The safety bar is thereby biased towards the bridle shaft the instant the operator operates the brake means to stop the movement of the draw cable in response to his observation that the boom begins to pivot freely.

The safety device of this invention is constructed of easily available and economically manufactured components. Its cost is therefore relatively low compared to the advantages gained. In addition, the invention is adapted to be added to already existing cranes whereby the safety with which existing cranes are operated can be improved with relatively little cost.

The various embodiments of this invention make it possible for use in conjunction with a variety of differently constructed boom cranes such as boom cranes provided with pivotal gantry masts and boom cranes provided with a bridle freely suspended between adjacent ends of the draw cable and the extender cable.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary side elevational view of the boom crane provided with a safety device constructed according to this invention;

FIG. 2 is a fragmentary, enlarged cross-sectional view taken along line 22 of FIG. 1;

FIG. 3 is a fragmentary side elevational view of the modification of the structure shown in FIG. 1;

FIG. 4 is a fragmentary, enlarged cross-sectional view taken along line 44 of FIG. 3;

FIG. 5 is a fragmentary side elevational view of another embodiment of this invention; and

FIG. 6 is a fragmentary, enlarged cross-sectional view taken along line 66 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, a boom crane 10 is shown mounted on a suitable support 12. The support may be fixed at a particular location or it may be part of a truck (not shown) provided with wheels (not shown) to facilitate the transportation of the crane.

The crane includes a platform 14 which is pivotally mounted on support 12 by means of vertical king pin 16 and which includes a suitable housing 18. Conventional drive means, motors and ballast (not shown) are mounted on the platform within the housing. One end of the platform includes a pair of upright, parallel and spaced-apart brackets 20 which extend in an outward direction from the platform and receives a pair of parallel, transverse pins 22 and 24. Pin 22 pivotally secures a boom 26 to mounting bracket 20 such that the boom is pivotable in a substantially vertical plane. Pin 24 pivotally secures a gantry mast 28 to the mounting bracket, the gantry mast being pivotable in the same plane as is the boom.

A free end 30 of the boom receives a peak sheave 32 which is rotatably mounted on a shaft 34 secured to the end of the boom. A load carrying cable 36 is guided over the peak sheave such that one end thereof, which end receives a swivel 38 provided with a hook 40, hangs vertically downward from the sheave. The other end of the load carrying cable 36 is engaged by a motorized cable drum 43 mounted on platform 14 within housing 18.

An extender cable 44 is secured to each end of shaft 34 adjacent the free end 30 of the boomby an eyelet 46. The opposite end of the extender cables are similarly secured to a transverse shaft 48 mounted adjacent a free end 50 of the gantry mast 28.

A block hoist includes pulleys 52 suitably mounted adjacent the free end 50 of the gantry mast 28 and which guide a draw cable 54, one end of which is engaged by a cable drum 56 mounted on platform 14 within housing 18. The draw cable permits the raising or lowering of the boom. Rotation of the cable drum 56 in a counter-clockwise direction, as viewed in FIG. 1, retracts the draw cable and pivots the gantry mast in a counter-clockwise direction on transverse pin 24. This movement of the gantry mast is transmitted to the free end 30 of boom 26 which in turn pivots on transverse pin 22. The free end of the boom is thereby raised such that hook 40 is moved in both a vertical and a horizontal direction. By rotating drum 56 in a clockwise direction, as viewed in FIG. 1, the boom is lowered.

Repeated operation of the draw cable and heavy loads exerted on it, such as when the draw cable i extended at a rapid rate and then instantaneously stopped, causes it to wear substantially, especially portions of the cable being repeatedly flexed around pullys 52. Imposition of an extremely heavy load after the cable has worn, may cause it to break. Breakage of the draw cable releases the constraint exerted by it on the gantry mast which, together with boom 26, is free to pivot in a clockwise direction as viewed in FIG. 1, until the boom contacts the ground underlying it. Serious injury to personnel positioned in the vicinity of the boom, as well as to property positioned there, and to the boom itself may ensue. To prevent the boom from dropping to the ground when the draw cable breaks, a safety bar 58 provided with a plurality of longitudinally spaced dogs 60 is provided.

The safety bar is pivotable on an axis substantially parallel to the axis of transverse pins 22 and 24 around a pin 62 which is suitably connected to platform 14. If the crane is provided with a gantry mast 28 as shown in FIG. 1, pin 62 is preferably mounted atop housing 18 by means of a structure (not shown) which is secured to the platform.

In a preferred embodiment of this invention, wherein two laterally spaced gantry masts are connected by means of a transverse crossbar 64, a pair of spaced-apart, substantially parallel and vertically extending support plates 66 are connected with the free ends 50 of the gantry masts. If the gantry mast can be telescoped the support plates 66 are secured to the trans-verse crossbar such that they do not interfere with the gantry mast when it is being retracted (see FIG. 2). If, on the other hand, the gantry mast is of the fixed type, the support plates can be secured directly to the upper free ends thereof. The support plates include a transversely mounted bridle shaft 68 which rotatably mounts the draw cable pulleys 52. The ends of the "bridle shaft extend beyond the support plates 66. The support plates are preferably welded onto the free ends of the gantry masts and, for large size cranes, are provided with crossbars 70 disposed intermediate the support plates for imparting rigidity onto the plates. In this embodiment of the invention, the safety bars 58 include a vertically disposed side member 72 and, joined thereto, a transverse track 74 including a lip 76 adjacent a side of the track opposite the side joined to the side member of the safety bar. The side member includes a plurality of recessed notches 78, the sides of which are inclined to the longitudinal axis of the safety bar and which define the plurality of dogs 60. If the notches, or dogs, have inclined sides, the bridle shaft 68 is more positively anchored when it is engaged by the dogs.

Attached to each support plate 66 and above the safety bars 58, are mounting brackets 80 which extend outwardly transverse to the plates. One end of a leaf spring 82 is suitably secured to each mounting bracket, the other end of the spring being provided with a pair of laterally spaced lugs 84 which receive a shaft 86 on which a wheel 88 is rotatably mounted. The mounting bracket, the leaf spring and the wheel are arranged so that the wheel engages an upper surface 90 of the track 74 and biases the track and the safety bar toward the bridle shaft 68. The notches '78 in the safety bar are thereby biased toward the bridle shaft and the safety bar engages the bridle shaft with one of the dogs 60. The bridle shaft, together with the support plates 66, the gantry mast 28 and the boom 26 are thereby constrained from pivoting in a clockwise direction, as viewed in FIG. 1, under their own weight and when the draw cable 54 fails.

Mounted on the support plate 66 intermediate the safety bar 58 and the free end 50 of the gantry mast 28 is a hydraulic actuator 92 comprising a cylinder 94 secured to the support plate, a piston 96 disposed within the cylinder and a piston rod 98 secured to the piston and extending toward the safety bar. The end of the piston rod opposite the end secured to the piston rotatably mounts a wheel 100. The cylinder and the piston rod are constructed and arranged such that when the piston is moved to an end of the cylinder adjacent the safety bar 58, wheel 100 biases the safety bar in opposition to the spring biased wheel 88 in a direction away from the bridle shaft 68 an amount sufficient to disengage dogs 60 from the bridle shaft. When piston 96 is permitted to move in a direction towards and adjacent to an end of cylinder '94 remote from the safety bar, leaf spring 82 biases the safety bar towards the bridle shaft 68 by means of wheel 88 such that one of the dogs 60 engages the ends of the bridle shaft extending past the support plates 66.

FIGS. 3 and 4 show a modification of the embodiment of this invention shown in FIGS. 1 and 2. As best seen in FIG. 4, the free ends 50 of the pair of laterally spaced, parallel gantry masts 28 are connected by a bridle shaft 102, which bridle shaft is shown to mount a pair of pulleys 52 over which the draw cable 54 is guided. An extender cable 104 is secured to the bridle shaft 102 by means of an eyelet 106 to constrain the free end of the boom 26 (not shown in FIGS. 3 and 4) to the free end 50 of the gantry masts.

A generally U-shaped support plate 108 is suitable secured to free end 50 of the gantry masts, such as by welding it thereto, the U-shaped support plate having a flat center portion 110 which is substantially parallel to the axis of bridle shaft 102. A safety bar 112, including a transverse track 114 is constructed identically to safety bar 58 shown in FIGS. 1 and 2, and is disposed intermediate the flat center portion 110 and bridle shaft 102. A leaf spring 116 is suitably secured to the flat center portion of the U-shaped member 108 and rotatably mounts a wheel 118 engaging an upper surface 120 of the track 114. The spring thereby biases the safety bar in a direction towards the bridle shaft 102 such that one of the dogs 60 engages the bridle shaft 102 intermediate the pulleys 52. To increase the effectiveness of the leaf spring 116, a wedge 121 is disposed intermediate the spring and the flat center portion 110.

Also secured to the flat center portion of the U-shaped support plate 108 is an hydraulic actuator 122 which has a configuration identical to that of the actuator 92 shown in FIG. 1 and which mounts a wheel 124 on a transverse shaft 126 secured to the piston rod 98. The hydraulic actuator 122 includes a piston 96 and a piston rod 98 which are constructed and arranged such that wheel 124 engages the track 114 intermediate the side member 72 and lip 76 and biases the safety bar in opposition to the spring loaded wheel 118 in a direction away from the bridle shaft 102. Release of the pistons holding force enables the leaf spring 116 to bias the safety bar 112 in a direction towards the bridle shaft until one of the dogs 60 engages the bridle shaft.

Hydraulic lines 92' suitably connect the cylinder 94 of the actuator 92, shown in FIG. 1, with brake means 56 associated with the drum 56 of the crane located within housing 18. Similar lines (not shown) connect the cylinder 122 of FIG. 3 to the brake means when that embodiment is used. An operator of the crane can thereby selectively move piston 96 disposed within the cylinder in one or the other direction to engage or disengage the safety bar from the bridle shaft by operating the brake means. Preferably, the hydraulic lines 92' are connected with the brake means disposed adjacent cable drum 56 located in housing 18 as shown and described and used to retract or extend draw cable 54. If the brake on the cable drum 56 is hydraulically releasable, the hydraulic actuator adjacent the safety bar is preferably directly coupled with it. They are coupled so that release of the brake automatically activates the hydraulic cylinder to bias the safety bar away from bridle shafts 68 or 102. If the brake adjacent the cable drum 56 is mechanically actuated, a suitable valve (not shown) is located adjacent to and activated by the means (not shown) for releasing the mechanical brake. A source of pressurized fluid (not shown) is generally available in motorized boom cranes. If, however, such source is not present, a readily available auxiliary pressurized fluid source can be installed on the crane at a suitable location.

While the crane is not in operation and all systems are deactivated, no pressurized fluid is present in cylinder 94. The leaf spring 82 or 116, respectively, biases the safety bar 58 or 112, respectively, in a direction towards the bridle shaft 68 or 102, respectively. The bridle shaft is engaged by one of the dogs 60 in the side member 72 of the safety bar which extends towards the bridle shaft. The gantry masts and with it the boom 26, since it is connected with the gantry masts by the extender cable 44, is positively prevented from pivoting in a downward direction even if the draw cable 54 or the brake 56' of cable drum 56 fails. The crane can be safely stored overnight without the necessity of having to lower the boom until it contacts the ground or a supporting member (not shown), which is frequently inconvenient or impossible because of space limitations at construction sites.

When the hydraulic fluid system is energized and the crane is to be operated to raise or'lower the boom, the operator releases the brake 56 on the cable drum 56 and retracts or extends the draw cable 54. Release of the brake simultaneously introduces pressurized fluid into the cylinder 94 whereby the piston 96 moves piston rod 96 and the safety bar 58 or 112, respectively, in a direction to disengage the dog 60 from bridle shaft 68 or 102. The safety bar is thereby moved in opposition to the force exerted by leaf spring 82 which biases the safety bar toward the bridle shaft. Upon cessation of the raising or lowering operation, the controls are actuated to again set the brakes 56 on the cable drum 66, which deenergizes the hydraulic actuator 92 and enables leaf spring 82 to bias the safety bar towards the bridle shaft 68 until one of the dogs 60 engages the bridle shaft and prevents it, together with the gantry mast 28 and boom 26, from pivoting in a clockwise direction, as viewed in FIG. 1.

The danger of breakage of draw cable 54 while the safety bar engages the bridle shaft is substantially eliminated. Should the draw cable break while the boom is being raised or lowered and while the safety bar is disengaged from the bridle shaft, and the cylinder is pressurized to bias the safety bar in opposition to the spring force, the operator observes the movement of the boom in a clockwise direction towards the ground under its own weight and under the weight of any load suspended on hook 40. As soon as he observes such movement, he sets the brake on the cable drum 56 which, since the cable is broken, is ineffectual in preventing the boom from dropping towards the ground. This attempt to set the brake 56', however, depressurizes the fluid in cylinder 94 whereby the leaf spring 82 biases the safety bar in a direction towards the bridle shaft. One of the dogs 60 of the safety bar thereby engages the bridle shaft and prevents it together with the gantry mast and the boom, from pivoting further in a downward direction. The danger of the boom, together with any load suspended from hook 40, from dropping to the ground which can cause substantial damage to life and property, is thereby substantially eliminated.

It is preferred to construct the hydraulic actuator 92 and the leaf spring such that the safety bar 58 disengages the bridle shaft 68 before the brake 56' fully releases cable drum 56. For example, if a hydraulic pressure of say 700 pounds per square inch is required to fully release the drum, the hydraulic actuator should bias the safety bar away from the bridle shaft at about one-half that pressure. This assures that the safety bar is disengaged from the bridle shaft even if the drum rotates before the brake has been fully released.

FIGS. 5 and 6 show another preferred embodiment of this invention installed on a boom crane having a platform 132 and a housing 134. A boom 136 is pivotally secured to a pair of laterally spaced mounting brackets 138 by a transverse pin 140. The free end of the boom also includes a peak sheave 32 rotatably mounted on a shaft 34 secured to the boom, which shaft further secures eyelets 46 of the extender cable 44. The extender cable, however, is secured to a bridle 142 comprising a pair of parallel, spaced-apart plates 144 which rotatably mount pulleys 146 over which a draw cable 148 is guided. A cable drum 150 is mounted interiorly of housing 134 and is motorized to extend or retract the draw cable whereby the boom is raised or lowered.

Atop the lower plate of the pair of plates 144 are a pair of spaced-apart mounting brackets 152 which are provided with coaxial holes 154 for mounting a bridle shaft 156 having an axis substantially parallel to the axis of transverse pin 140.

A pair of safety bars 158 are pivotally secured to a pair of mounting brackets 157 disposed on top of the cranes operator cabin by means of a transverse pin 159 which is parallel to transverse pin 140. The safety bars have a generally rectangular cross-section and are provided with a plurality of recessed notches 160 which define a plurality of longitudinally spaced dogs 162 facing towards the bridle shaft 156.

The safety bar is tapered adjacent its free end 163 as shown in FIG. to facilitate the transportation of the crane when the boom 136 and the safety bar are in a substantially horizontal position. To increase the rigidity of the pair of safety bars their free ends 163 are preferably connected to each other by a crossbar 164.

A guide bar 165 is laterally spaced from safety bar 158 and is secured thereto by means of a pair of generally U- shaped holders 166, one holder being located adjacent each end of the guide bar. Sides 168 of the holder preferably include elongated notches 170, the notches being elongated in a direction transverse to the safety bar 158 and the guide bar 165, to engage a transverse pin 172 secured to the guide bar. The guide bar is thereby movable relative to the safety bar 165 in a direction towards and away from the safety bar within the confines of the notches 170. The holders 166 and the notches 170 are constructed such that the bridle 142 is disposed intermediate the guide bar and the safety bar. When the pin 172 is adjacent the end of notch 170 remote from the safety bar the dogs 162 are disengaged from the bridle shaft because the weight of the safety bar pivots it downwardly while the guide bar continues to be supported by the upper plate 144 of the bridle 142. If the pin 172 is adjacent the end of the notch proximate to the safety bar, the safety bar is biased toward the guide bar 165 until the bridle shaft engages one of the notches 160 in safety bar 158. The upper plate of the pair of plates 144 receives pairs of laterally spaced guide strips 173 which engage the guide bars 165 and prevent lateral movement between the guide bars and the bridle 142. Portions of the guide strips 173 are preferably raised to receive a transverse shaft 173A to constrain the bridle to the guide bar 165.

Ends of a pair of cantilever springs 174 are secured to ends of each guide bar 165, engage the holders 166 and bias the guide bar in a direction towards upper plate 144 of the bridle 142 and the safety bar whereby the safety bar is biased in a direction towards the bridle shaft. Adjusting bolts 175 are threadably secured to ends of the holders 166 to permit adjustment of the force exerted by cantilever springs 174.

Hydraulic actuators 176 are disposed on each end of the guide bar and comprise a cylinder 178, a piston 180, and a piston rod 182 secured to the piston. The cylinder is suitably secured to the safety bar and the free end of the piston rod is secured to the guide bar such that the guide bar is biased in opposition to the force exerted by leaf springs 174 when the piston is in a position adjacent the end of the cylinder facing towards the guide bar. A space 183 is disposed intermediate the end of cylinder 178 adjacent the safety bar 158 and the safety bar when the cylinders are mounted on the edge of the safety bar facing the guide bar and the free end 163 of the safety bar is tapered as shown in FIG. 5. Identical cylinders 178 can be used on both ends of the safety bar.

A support block 185 is secured to boom 136 intermediate its ends and extends upwardly toward the safety bar 158. When the crane is being transported between construction sites and the boom is lowered into a substantially horizontal position the free end 163 of the safety bar rests on the support blocks. Substantial stresses in the draw cable during transportation resulting from holding the safety bar 165 and the bridle 142 in a substantially horizontal position are thereby eliminated.

The safety device of this embodiment operates in a manner similar to that described in conjunction with the description of FIG. 1 of the preferred embodiment of this invention. The cylinders 178 are connected with hydraulic lines (not shown) which communicate with a source of pressurized hydraulic fluid (not shown). Pressurized fluid is introduced into the cylinders such that th pistons are moved in a direction towards the guide bar 165 while the cable drum is being rotated and the brakes (not shown) of the cable drum are released. The safety bar thereby pivots downwardly under its own weight and dogs 162 of the safety bar are disengaged from the bridle shaft 156. Upon setting of the brake, in response to breakage of the draw cable or to deactivate the cable drum 150, the hydraulic cylinder 178 is depressurized, permitting cantilever spring 174 to bias the guide bars in a direction towards the safety bars 158. One of the dogs 162 of each safety bar then engages the ends of the bridle shaft. The mounting bracket together with the extender cable and the boom 136 are thereby prevented from pivoting in a clockwise (as seen in FIG. 5) and downward direction.

The safety device of this invention can be installed on new as well as on presently used boom cranes. Its installation is easy and relatively inexpensive, especially when compared with its capability of preventing substantial and serious damages to human life to property. It is more over adapted for use in conjunction with all varieties of cranes having a raisable boom.

I claim:

1. In a crane including a platform, a raisable boom having one end pivotally secured to the platform, an extender cable secured to the boom adjacent a free end of the boom, means for raising and lowering the boom, and bridle means including a bridle shaft for coupling the extender cable and the means for raising and lowering the boom, the improvement comprising (a) an elongated safety bar connected to the platform,

extending past adjacent the bridle shaft and provided with a plurality of longitudinally space dogs facing toward the bridle shaft,

(b)hmeans biasing the safety bar toward the bridle s aft,

(0) means biasing the safety bar in opposition to the means biasing the safety bar toward the bridle shaft such that the safety bar and the bridle shaft are disengaged, and

(d) control means connected to the opposing biasing means for reducing the opposing bias condition such that the safety bar and bridle shaft are allowed to engage.

2. Apparatus according to claim 1, wherein said control means comprises brake means operatively connected with said means for raising and lowering the boom.

3. Apparatus according to claim 1 wherein the bridle means are mounted on a gantry mast pivotally connected with the platform and including support means secured to the gantry mast for mounting the means for biasing the safety bar toward the bridle shaft and the means for biasing the safety bar in opposition.

4. Apparatus according to claim 3 wherein the safety bar includes elongated track means and wherein the means for biasing the safety bar toward the bridle shaft include a spring connected with the support means.

5. Apparatus according to claim 4 wherein the means for biasing the safety bar in opposition include a hydraulic actuator secured to the support means and means movably engaging the track means and connected with the hydraulic actuator for biasing the safety bar in opposition to the spring.

6. Apparatus according to claim 5 wherein the support means include a pair of laterally spaced support plates secured to a free end of the gantry mast, the support plates extending upwardly in planes substantially transverse to an axis of the bridle shaft and wherein the bridle shaft is mounted intermediate the plates.

7. Apparatus according to claim 6 wherein one safety bar is positioned adjacent each plate.

8. Apparatus according to claim wherein the bridle shaft is secured to a free end of the gantry mast and wherein the support means include a support plate connected with the gantry mast adjacent the free end of the gantry mast, the support plate having a portion positioned substantially parallel to the bridle shaft.

9. Apparatus according to claim 1 wherein the means for biasing the safety bar toward the bridle shaft include an elongated guide bar laterally spaced from and biased toward the safety bar and wherein the bridle shaft is disposed intermediate the safety bar and the guide bar.

10. Apparatus according to claim 9 including holding means movably restraining the guide bar to the safety bar such that the guide bar is laterally movable toward and away from he safety bar and a spring engaging the guide bar and secured to the holding means for biasing the guide bar toward the safety bar.

11. Apparatus according to claim 10 wherein the means for biasing the safety bar in opposition include a hydraulic actuator disposed intermediate the guide bar and the safety bar.

12. Apparatus according to claim 11 wherein one safety bar is positioned adjacent each end of the bridle shaft and including means to connect free ends of the safety bars to each other.

13. A crane comprising:

(a) a platform,

(b) a raisable boom having one end pivotally connected with the platform,

(c) an extender cable secured to the boom adjacent a free end of the boom,

(d) means including a draw cable for raising and lowering the boom,

(e) bridle means mounted on a pivotable gantry mast and including a bridle shaft for coupling the extender cable and the draw cable,

(f) an elongated safety bar pivotally connected with the platform, extending past adjacent the bridle shaft and provided with a plurality of longitudinally spaced dogs facing toward the bridle shaft, the safety bar being provided with an elongated track,

(g) a support plate adjacent the bridle shaft and secured to a free end of the gantry mast,

(h) a hydraulic cylinder secured to the support plate and having a piston and a piston rod extending toward the safety bar for biasing the piston in a direction toward the safety bar,

(i) a first roller rotatably secured to the piston rod and in engagement with one side of the guide track,

(j) a spring secured to the support plate,

(k) a second roller rotatably secured to the spring and engaging a side of. the guide track opposite the side engaged by the first roller, and

(l) brake means operatively connected with said means for raising and lowering the boom, said hydraulic cylinder being operatively connected to said brake means and disabled when said brake means is applied to said means for raising and lowering the boom.

14. A crane comprising:

(a) a platform,

(b) a raisable boom having one end pivotally connected with the platform,

(c) an extender cable secured to the boom adjacent a free end of the boom,

(d) means including a draw cable for raising and lowering the boom,

(e) bridle means for coupling the extender cable and the draw cable,

(f) a bridle shaft secured to the bridle means, an axis of the bridle shaft being substantially transverse to a plane in which the boom pivots,

(g) an elongated safety bar pivotally connected with the platform, extending past adjacent the bridle shaft and provided with a plurality of longitudinally spaced dogs facing toward the bridle shaft,

(11) an elongated guide bar laterally spaced from the safety bar adjacent the bridle shaft and opposite from the safety bar,

(i) holding means for movably securing the guide bar to the safety bar such that the guide bar is movable toward and away from the safety bar,

(j) spring means for biasing the guide bar toward the safety bar,

(k) hydraulically actuated means for biasing the guide bar in opposition to the spring, and

(l) brake means operatively connected with said means for raising and lowering the boom, said hydraulically actuated means being operatively connected to said brake means and disabled when said brake means is applied to said means for raising and lowering the boom.

15. Apparatus according to claim 14 wherein the spring means comprise a leaf spring disposed intermediate the guide bar and the holding means and secured to the holding means.

16. Apparatus according to claim 15 wherein the hydraulically actuated means include a cylinder secured to the safety bar, a piston and a piston rod secured to the guide bar.

- References Cited UNITED STATES PATENTS 1,396,250 11/1921 Burke 212-59 2,198,793 4/ 1940 Schroeder 212-59 FOREIGN PATENTS 1,169,630 5/ 1964 Germany.

1,218,128 6/1966 Germany.

HARVEY C. HORNSBY, Primary Examiner US. Cl. X.R. 212.8, 59, 144 

